Chester’s system would require at least two measures of student learning when evaluating teachers. One would be student gains on the statewide MCAS exams. Others could include samples of student work, other commercially available assessments, or tests designed by individual districts or academic departments.

Nothing trumps good teaching. Effective teachers routinely impart a year-and-a-half-gain in student achievement over the course of a single academic year. Three or four consecutive years of exposure to that level of instruction can eradicate the achievement gap between low-income and high-income students. Bad teachers routinely secure just a half-year of student progress over the same period. A few years of that kind of instruction can lead to academic ruin.

Current union contracts or traditions in many urban school districts prohibit administrators even from making unannounced classroom visits for the purpose of collecting data for teacher evaluations. Chester is trying to end this standoff by taking a high-minded approach to teacher evaluations. He’s demanding proficiency of teachers in curriculum planning, instruction, family engagement, and collegiality. But he is also offering pathways for shaky teachers to improve while making it clear that one year of such efforts is all any school can endure before a poorly performing teacher is terminated.

Even if Chester’s proposal wins approval from the state Board of Education, districts will still have great latitude in determining how much weight should be given to MCAS scores when evaluating teachers. Hard-headed business leaders want student test scores to count for half of a teacher’s evaluation. But Chester is right to allow the districts to figure out the proportions for themselves. His proposal is specific enough to guarantee rigorous evaluations, but open-ended enough to allow districts with different problems to contour the criteria to their needs.

The public will get a chance to evaluate teachers and their union leadership by how they respond to this proposal. Embracing it would be exemplary. Rejecting it or trying to water it down in collective bargaining would rate a resounding F.